fcos

Cosine

FCOS

Computes cosine of ST(0) (in radians).

Details

Computes the cosine of ST(0), where the argument is interpreted as an angle in radians. The result replaces ST(0); the x87 FPU status flags are updated. This transcendental instruction may set the C2 flag if the argument exceeds the acceptable range.

Pseudocode Operation

ST(0) ← cos(ST(0))

Example

FCOS

Encoding

Binary Layout

Format Legacy

Opcode D9 FF

Extension x87 FPU

Operands

Reference (Intel® SDM)

Instruction Forms

Opcode	Instruction	Op/En	64/32-bit Mode	CPUID	Description
D9 FF	FCOS		Valid Valid		Replace ST(0) with its approximate cosine.

Description

Computes the approximate cosine of the source operand in register ST(0) and stores the result in ST(0). The source operand must be given in radians and must be within the range −263 to +263. The following table shows the results obtained when taking the cosine of various classes of numbers. Table 3-25. FCOS Results ST(0) SRC ST(0) DEST − ∞ * − F −1 to +1 − 0 + 1 + 0 + 1 + F − 1 to + 1 + ∞ * NaN NaN

Operation

IF |ST(0)| < 263
THEN
C2 := 0;
ST(0) := FCOS(ST(0)); // approximation of cosine
ELSE (* Source operand is out-of-range *)
C2 := 1;
FI;





FCOS—Cosine                                                                                                                                      Vol. 2A 3-330

Exceptions

Protected Mode Exceptions

#NM CR0.EM[bit 2] or CR0.TS[bit 3] = 1. #MF If there is a pending x87 FPU exception. #UD If the LOCK prefix is used.

Real-Address Mode Exceptions

Same exceptions as in protected mode.

Virtual-8086 Mode Exceptions

Same exceptions as in protected mode.

Compatibility Mode Exceptions

Same exceptions as in protected mode.

64-Bit Mode Exceptions

Same exceptions as in protected mode. FCOS—Cosine Vol. 2A 3-331